The Design of High Efficiency Crossflow Hydro Turbines: A Review and Extension

Abstract

Efficiency is a critical consideration in the design of hydro turbines. The crossflow turbine is the cheapest and easiest hydro turbine to manufacture and so is commonly used in remote power systems for developing countries. A longstanding problem for practical crossflow turbines is their lower maximum efficiency compared to their more advanced counterparts, such as Pelton and Francis turbines. This paper reviews the experimental and computational studies relevant to the design of high efficiency crossflow turbines. We concentrate on the studies that have contributed to designs with efficiencies in the range of 88-90%. Many recent studies have been conducted on turbines of low maximum efficiency, which we believe is due to misunderstanding of design principles for achieving high efficiencies. We synthesize the key results of experimental and computational fluid dynamics studies to highlight the key fundamental design principles for achieving efficiencies of about 90%, as well as future research and development areas to further improve the maximum efficiency. The main finding of this review is that the total conversion of head into kinetic energy in the nozzle and the matching of nozzle and runner designs are the two main design requirements for the design of high efficiency turbines.

The Performance Characteristics of The Low Head Cross Flow Turbine Using Nozzle Roof Curvature Radius Centered on Shaft Axis

“…The collision results in the existence of hydraulic loss and direction changing of water jets towards the second stage. In addition, in this experimental study, thesmall amount of water leakage through the gap between runner disk and nozzle wall is considered negligible [21].Further, in order to harness water power efficiently by minimizing hydraulic loss and water leakage, it is reccomended to use the cross flow turbine with nozzle entry arc of 90 o or 75 o rather than using the cross flow turbine with nozzle entry arc of 120 o .…”

“…The maximum efficiency of the turbine models were achieved at the U/V of about 0.73.The highest efficiency of about 0.79 is for the model with 75 o and that with 90 o nozzle entry arcs, and the highest efficiency of 0.68 is for the model with 120 o nozzle entry arc.According to the basic principle of rotating machines derived mathematically, the optimum efficiency occurring at the speed ratio is 0.5. There is a difference in value between the efficiency of theoretical and experimental efficiency, it is presumed that the existence of hydraulic losses when water flow mashing a number of active blades and the condition of the water flow in the empty space of the turbine wheel that collides with one another resulting in changes in the direction of the water flow towards the turbine blades of the second stage, the such conditionsof water flow resulted in the different efficiency of each examinedturbine model [21]. In addition, the larger the nozzle entry arc is, the more the number of water jet enters the runner, and consequently the larger entry arc is, the more the water collisioninside the runner that causes hydraulic losses [21].These losses result in different efficiencies of the models as reported above.…”

“…The turbine performance can be observed based on the head and the capacity of the water flow towards the power generation of the axis and the turbine efficiency [11]. The turbine performance can also be seen from the velocity, the flow rate comparison, and the specific rotation of the turbine operation [21]. Based on the correlation of these variations towards the turbine performance, it will be obtained the comparison or performance difference of the cross-flow turbine which is designed with the same head, capacity, and turbine wheels diameter but with different angle of jet arc.…”

Simulations of Bio-Micro High Power Density Power Generation System for Zero Energy Building

“…The main design parameters such as temperature, pressure, flow rate, and geometry as well are many analyzed, refers to the constraint of dimension and operating condition. The potential head conversion had been reviewed as one of the crucial parameters for high-efficiency impulse turbine (Adhikari & Wood, 2018) The maximum effective velocity had been extracted from enthalpy drop in combustion much affected by the proper geometrical design (Belega & Nguyen, 2015).…”

Computational Analysis of a Double-Nozzle Crossflow Hydroturbine

“…Although Desai [5] and Totapally and Aziz [6] achieved a maximum efficiency η max of 88% and 90% respectively for a small-scale 0.53 kW turbine through extensive experimental development, no larger turbines of similar performance have been built and tested. We speculate that this is due to a lack of understanding of the design principles for achieving high efficiency, as developed by Adhikari and Wood [7] for the nozzle and by Adhikari and Wood [8] for the nozzle and the runner designs.…”